Incomplete Phase Metasurface for Wavefront Reconstruction

Metasurfaces consisting of subwavelength elements exhibitunparalleledflexibility in light manipulation in terms of phase, amplitude, and/orpolarization at ultrathin dimensions. Typically, a continuous andcomplete phase distribution covering a full 2 & pi; range is requiredin metasurface design to produce the performance of conventional opticalcomponents, such as gratings, lenses, and beam splitters. However,an incomplete phase, i.e., with phase change less or larger than 2 & pi;,can provide additional degrees of freedom for optical wavefront reconstruction.This article shows that designed metagratings, which unlocked the2 & pi; phase constraint in supercell designs, achieved arbitrarycontrol of the intensity ratio between any adjacent diffraction orders,while keeping the diffraction directions consistent with those ofconventional gratings. Four metagratings, as representatives, withdifferent phase ranges in the supercell, i.e., & pi;, 2 & pi;,3 & pi;, and 4 & pi;, have been designed and fabricated to demonstratethe diffraction intensity redistribution capability of metagratings.The 0th- and the 1st-order splitting ratios measured in experimentscan reach 0.07 to 24.8, which is a hard task for traditional gratingdevices. Using a simple design methodology, incomplete phase metasurfaceshold great promise for developing various functional ultrathin nanophotonicdevices, such as controllable beam splitters, spectrometers, and multifocimetalens.

Automated summary

Metasurfaces composed of subwavelength elements can flexibly manipulate light in terms of phase, amplitude, and polarization at ultrathin dimensions. This article demonstrates that designed metagratings, which overcome the 2π phase constraint, allow for arbitrary control of the intensity ratio between adjacent diffraction orders while maintaining consistent diffraction directions. Incomplete phase metasurfaces hold great potential for developing various ultrathin nanophotonic devices with functionalities such as controllable beam splitters, spectrometers, and multifocal metalenses.